The present invention relates to vertical insulated gate field effect transistors (IGFETs) which can be used in integrated circuit applications. Additionally, it relates to a method for fabricating such devices in a relatively simple manner.
The term vertical IGFET, as used herein, refers to a device wherein the transistor current flow is regulated along a direction which is perpendicular to the major surfaces of the substrate on which the device is disposed. Source, body and drain regions of the transistor are in an overlying relationship to one another, and an insulated gate substantially surrounds, and is contiguous with the body region. When the insulated gate is appropriately electrically biased, a conduction channel is formed between the source and drain regions in that portion of the body region adjacent to the insulated gate.
The vertical configuration of the source, body and drain regions in such a vertical IGFET intrinsically consumes less substrate surface area than does a lateral configuration. Thus, if the source, body and drain regions can be made suitably small, the resulting structure might advantageously be used in integrated circuits, where device packing density is a important consideration.
A vertical IGFET and the epitaxial lateral overgrowth (ELO) fabrication method is disclosed in copending U.S. patent application Ser. No. 439,563, VERTICAL IGFET WITH INTERNAL GATE AND METHOD FOR MAKING SAME, S. C. Blackstone et al., filed Nov. 5, 1982, now abandoned. The device disclosed therein, the preferred embodiment of which incorporates a plurality of parallel gates, is particularly suitable to power switching applications. Photolithographic limitations constrain the spacing, i.e. the packing density between neighboring gates.
We have now discovered a method, which uses conventionally available processing techniques, whereby the spacing between gates can be reduced by greater than an order of magnitude. The recognition of this space-reducing method led to the realization of a device structure which is well suited to application in integrated circuits.